With the introduction of telematic systems, provision has been made, particularly in connection with navigation systems, which know the position of a vehicle, for a serious accident, in which injuries to the people in the vehicle involved in the accident can be expected, to automatically prompt an emergency call to be sent in order to save valuable time in rescuing the people involved in the accident. This is frequently done using mobile radio links.
In this case, it is necessary to ensure that the vehicles contain a suitable sensor system which, on the one hand, reliably prompts the sending of an emergency call in the event of a serious accident but, on the other hand, does not send any erroneous emergency calls, for example, when an accident does not actually arise following a critical driving situation. In this regard, various systems have already been proposed.
EP 1 372 324 A2, which is incorporated herein by reference, describes a portable radio communication terminal which has a radio transmitter and receiver, a microphone, a loudspeaker and a light emitter. In the normal mode of operation, activation of the system prompts the loudspeaker, the microphone and the light emitter to be switched on in order to allow communication with a preselected call center. In a static mode of operation, the loudspeaker and the light emitter are switched off and the microphone is switched on in the event of activation so that the user can inform the call center about his state even in a situation in which he is no longer readily able to operate the appliance.
DE 10 2005 018 234 B3, which is incorporated herein by reference, discloses emergency systems in which, in the event of a hazard situation, a first hazard message with the position of the vehicle is reported to a control center. If the outcome of this hazard message is not an accident, an all-clear message is sent shortly afterwards. This practice is highly prone to trouble, however. In addition, it is known practice to ascertain the degree of probability of an accident and to use it as a limit value for sending an emergency signal. When the emergency call has been sent, a timer is activated. If there is no specific accident message available when the timer runs out, the emergency call is automatically revoked. A proposed system which is totally independent of the vehicle electronics is an emergency system which detects the release of an airbag using a microphone and possibly independently discharges an emergency call.
DE 43 21 416 A1, which is incorporated herein by reference, discloses a vehicle emergency system in which the vehicle is equipped with an active position-finding device, with a crash sensor and with an emergency transmitter. The position finding device continually ascertains the current position of the vehicle and transmits it to the emergency transmitter, which stores the position until a more up-to-date position is transmitted. In the event of an accident, the crash sensor checks whether an emergency call needs to be sent, and releases the emergency call if appropriate. The emergency transmitter then transmits the emergency call with the currently stored position.
A drawback of this is that the transmission of the emergency call is prompted by a crash sensor, typically the airbag sensor, which means that if there is a fault in the sensor then no emergency call is transmitted. In addition, to prevent false alarms, the initiation threshold needs to be set very high. This has the result that in some emergency situations, in which the sensor (still) does not initiate, no emergency call is transmitted even though this would be appropriate. The other systems, in which just relatively low accident probability prompts emergency calls to be discharged which possibly need to be revoked, are not manageable in practice, since rescue centers need to react to an incoming emergency call immediately and cannot first await whether an emergency call is revoked.